Interactions of Herbicides with Photosynthetic Electron Transport

Weed Science ◽  
1991 ◽  
Vol 39 (3) ◽  
pp. 458-464 ◽  
Author(s):  
E. Patrick Fuerst ◽  
Michael A. Norman
Keyword(s):  
Electron Transport ◽  
Membrane Lipids ◽  
Electron Flow ◽  
Membrane Integrity ◽  
D1 Protein ◽  
Photosynthetic Electron Transport ◽  
Peroxidation Of Lipids ◽  
Ps Ii ◽  
Ps I ◽  
Sulfur Protein

The two primary sites of herbicide action in photosynthetic electron transport are the inhibition of photosystem II (PS II) electron transport and diversion of electron flow through photosystem I (PS I). PS II electron transport inhibitors bind to the D1 protein of the PS II reaction center, thus blocking electron transfer to plastoquinone. Inhibition of PS II electron transport prevents the conversion of absorbed light energy into electrochemical energy and results in the production of triplet chlorophyll and singlet oxygen which induce the peroxidation of membrane lipids. PS I electron acceptors probably accept electrons from the iron-sulfur protein, Fa/Fb. The free radical form of the herbicide leads to the production of hydroxyl radicals which cause the peroxidation of lipids. Herbicide-induced lipid peroxidation destroys membrane integrity, leading to cellular disorganization and phototoxicity.

Die Wirkung 2.3-substituierter Naphthochinone auf einzellige Algen und isolierte Spinatchloroplasten/ The Effect of 2,3-Substituted Naphthoquinones on Unicellular Algae and Isolated Spinach Chloroplasts

1979 ◽  
Vol 34 (11) ◽  
pp. 961-963 ◽  
Author(s):  
Klaus Bauer ◽  
Helmu Kodier
Keyword(s):  
Electron Transport ◽  
Dark Respiration ◽  
Electron Flow ◽  
Photosynthetic Electron Transport ◽  
Flow Mode ◽  
Ps Ii ◽  
Spinach Chloroplasts ◽  
Ps I ◽  
Low Concentrations ◽  
Strong Stimulation

Abstract Short term effects of 2-(C-dichloro-acetylamino)-3-chloro-1,4-naphthoquinone (Hoe 13465, quinonamid*) and 2-amino-3-chloro-1,4-naphthoquinone (Hoe 17399, 06K-quinone) on cell suspensions of Chlorella vulgaris, Anabaena flos aquae, Porphyridium cruentum, and on isolated spinach chloroplasts were studied. The results clearly show that both substances inhibit the photosynthetic O2 production of algal suspensions as well as the electron transport of PS II in spinach chloroplasts. PS I is not inhibited by the action of the two algicides. At low concentrations quinonamid acts as a photosynthetic electron transport blocker, whereas Hoe 17399 is a weak inhibitor of photosynthetic electron flow. Mode of action of the two naphthoquinones is discussed. Both naphthoquinone derivatives can operate as an electron acceptor for PS I at low concentra­tions (10-5-10-6м). In addition there is observed a strong stimulation of dark respiration in algal cells induced by both of the compounds, Hoe 17399 causes a much higher stimulation rate than quinonamid does.

Reinvestigation of the Effects of Disalicylidenepropanediamine (DSPD) and 2-Hepty-4-hydroxyquinoline-N-oxide (HQNO) on Photosynthetic Electron Transport

1981 ◽  
Vol 36 (1-2) ◽  
pp. 109-114 ◽  
Keyword(s):  
Electron Transport ◽  
Electron Flow ◽  
Photosynthetic Electron Transport ◽  
Reduced Form ◽  
Similar Extent ◽  
Ps Ii ◽  
Ps I ◽  
Inhibitory Site ◽  
High Concentrations ◽  
Dark Decay

Abstract The effects of disalicylidenepropanediamine (DSPD) and 2-heptyl-4-hydroxyquinoline-Noxide (HQNO) on photosynthetic electron transport have been reexamined. The results confirm earlier observations that lower concentrations of DSPD (< 100μᴍ) block electron transport at the levels of ferredoxin and plastocyanin. High concentrations of DSPD even inhibit electron transport from H2O → pBQ, suggesting that DSPD has an inhibitory site in PS II as well. Thermoluminescence curves of DSPD and DCMU treated chloroplasts were very similar, showing that the third inhibitory site of DSPD is similar to that of DCMU. Both oxidized and reduced HQNO, (0.6-6 μᴍ) blocked electron transport from H2O → pBQ, H2O → MV/FeCy to a similar extent. The effect of HQNO on thermoluminescence showed that its inhibitory site is probably located before that of DCMU. At higher concentration (> 6 μᴍ), the H2O → MV/FeCy reactions were more strongly inhibited by oxidized HQNO than those occuring from H2O → pBQ, suggesting that a new site of inhibition must also be considered. The dark decay of the P 700 signal was not influenced by the addition of oxidized HQNO which shows that the new inhibitory site of HQNO is located between plastoquinone and P 700. The reduced form of HQNO did not inhibit non-cyclic electron transport around PS I. Indeed, at higher concentrations, reduced HQNO even accelerates electron flow from DCIP → MV and the dark reduction of P 700, thus suggesting that this compound has a “donor-mediator” function in PS I.

Photoinactivation of Photosynthetic Electron Transport under Anaerobic and Aerobic Conditions in Isolated Thylakoids of Spinach

1992 ◽  
Vol 47 (1-2) ◽  
pp. 63-68 ◽  
Author(s):  
Rekha Chaturvedi ◽  
M. Singh ◽  
P. V. Sane
Keyword(s):  
Electron Transport ◽  
Photosynthetic Electron Transport ◽  
Oxygen Evolving Complex ◽  
Reaction Centre ◽  
Ps Ii ◽  
Ps I ◽  
S2 State ◽  
The Stability ◽  
Oxygen Evolving ◽  
Spinach Thylakoids

Abstract The effect of exposure to strong white light on photosynthetic electron transport reactions of PS I and PS II were investigated in spinach thylakoids in the absence or presence of oxygen. Irrespective of the conditions used for photoinactivation, the damage to PS II was always much more than to PS I. Photoinactivation was severe under anaerobic conditions compared to that in air for the same duration. This shows that the presence of oxygen is required for prevention of photoinactivation of thylakoids. The susceptibility of water-splitting complex in photoinactivation is indicated by our data from experiments with chloride-deficient chloroplast membranes wherein it was observed that the whole chain electron transport from DPC to MV was much less photoinhibited than that from water. The data from the photoinactivation experiments with the Tris-treated thylakoids indicate another photodam age site at or near reaction centre of PS II. DCMU-protected PS II and oxygen-evolving complex from photoinactivation. DCMU protection can also be interpreted in terms of the stability of the PS II complex when it is in S2 state.

Inhibition by Tetranitromethane of Photosynthetic Electron Transport from Water to Photosystem II in Chloroplasts

1980 ◽  
Vol 35 (3-4) ◽  
pp. 293-297 ◽  
Author(s):  
P. V. Sane ◽  
Udo Johanningmeier
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Electron Flow ◽  
Ph Dependence ◽  
Photosynthetic Electron Transport ◽  
Donor Side ◽  
Ps Ii ◽  
Diphenyl Carbazide ◽  
Low Concentrations ◽  
Sh Group

Abstract Low concentrations (10 µM) of tetranitromethane inhibit noncyclic electron transport in spinach chloroplasts. A study of different partial electron transport reactions shows that tetranitromethane primarily interferes with the electron flow from water to PS II. At higher concentrations the oxidation of plastohydroquinone is also inhibited. Because diphenyl carbazide but not Mn2+ ions can donate electrons efficiently to PS II in the presence of tetranitromethane it is suggested that it blocks the donor side of PS II prior to donation of electrons by diphenyl carbazide. The pH dependence of the inhibition by this protein modifying reagent may indicate that a functional-SH group is essential for a protein, which mediates electron transport between the water splitting complex and the reaction center of PS II.

The Inhibition of Photosynthetic Light Reactions by Halogenated Naphthoquinones

1981 ◽  
Vol 36 (7-8) ◽  
pp. 645-655 ◽  
Author(s):  
Klaus Pfister ◽  
Hartmut K. Lichtenthaler ◽  
Günther Burger ◽  
Hans Musso ◽  
Manuel Zahn
Keyword(s):  
Chlorophyll Fluorescence ◽  
Electron Transport ◽  
Binding Site ◽  
Chlorophyll A ◽  
Electron Flow ◽  
Photosynthetic Electron Transport ◽  
Ps Ii ◽  
Photosynthetic Electron Flow ◽  
A Site ◽  
Fluorescence Transients

Abstract Halogenated naphthoquinones act as inhibitors of photosynthetic electron flow. I50 concentra­ tion for inhibition of methylviologen reduction were found to range between 2 × 10-5 m to 2 × 10-6 M. Comparing their effects on several partial reactions of electron flow, the inhibition site of the naphthoquinones was found to be at the reducing site of PS II. Studies of fluorescence transients in presence of halogenated naphthoquinones give further evidence for a site action similar to that of diuron and different to that of DBMIB. All naphthoquinones act as quenchers of chlorophyll fluorescence with pure chlorophyll a, and with much higher efficiency in green algae and chloroplasts. It is concluded, that the halogenated naphthoquinones act similar to PS II-inhibitors like diuron, but do not share a common binding site at the PS II-complex. Implications of a possible involvement of phylloquinone K 1 in photosynthetic electron transport are discussed. The synthesis of 2-chloro-as well as 2-bromo-3-isopropyl-1,4-naphthoquinone is described.

scholarly journals Photosynthetic performance of Salvinia natans exposed to chromium and zinc rich wastewater

2008 ◽  
Vol 20 (1) ◽  
pp. 61-70 ◽  
Author(s):  
Bhupinder Dhir ◽  
P. Sharmila ◽  
P. Pardha Saradhi
Keyword(s):  
Electron Transport ◽  
Assimilation Efficiency ◽  
Carbon Assimilation ◽  
Photosynthetic Electron Transport ◽  
Redox Status ◽  
Photosynthetic Performance ◽  
Pyridine Nucleotides ◽  
Ps Ii ◽  
Ps I ◽  
Salvinia Natans

Investigations were carried out to evaluate alterations in photosynthetic performance of Salvinia natans (L.) exposed to chromium (Cr) and zinc (Zn) rich wastewater. Accumulation of high levels of Cr and Zn in plants affected photosynthetic electron transport. Photosystem- (PS) II-mediated electron transport was enhanced in plants exposed to Cr rich wastewater while a decline was observed in Zn-exposed plants. Photosystem-I-mediated electron transport increased in plants exposed to Cr and Zn rich wastewater. Efficiency of photosystem II (Fv/Fm) measured by fluorescence did not show any significant change in Cr-exposed plants but a decrease was observed in Zn-exposed plants as compared to the control. The enhancement in PS I-induced cyclic electron transport in Cr and Zn exposed plants led to a build up of the transthylakoidal proton gradient (DpH) which subsequently helped in maintaining the photophosphorylation potential to meet the additional requirement of ATP under stress. The carbon assimilation potential was adversely affected as evident from the decrease in Rubisco (EC 4.1.1.39) activity. The alterations in photosynthetic electron transport affected stromal redox status and induced variations in the level of stromal components such as pyridine nucleotides in plants exposed to Cr and Zn rich wastewater. The present investigations revealed that alteration in the photosynthetic efficiency of Salvinia exposed to Cr could primarily be the result of a decline in carbon assimilation efficiency relative to light-mediated photosynthetic electron transport, though in the case of Zn-exposed plants both these factors were affected equally.

Interaction of Photosystem II Herbicides with Bicarbonate and Formate in Their Effects on Photosynthetic Electron Flow

1984 ◽  
Vol 39 (5) ◽  
pp. 374-377 ◽  
Author(s):  
J. J. S. van Rensen
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Electron Flow ◽  
Photosynthetic Electron Transport ◽  
Hill Reaction ◽  
Amaranthus Hybridus ◽  
Apparent Affinity ◽  
Photosynthetic Electron Flow ◽  
Different Characteristics ◽  
The Hill

The reactivation of the Hill reaction in CO2-depleted broken chloroplasts by various concentrations of bicarbonate was measured in the absence and in the presence of photosystem II herbicides. It appears that these herbicides decrease the apparent affinity of the thylakoid membrane for bicarbonate. Different characteristics of bicarbonate binding were observed in chloroplasts of triazine-resistant Amaranthus hybridus compared to the triazine-sensitive biotype. It is concluded that photosystem II herbicides, bicarbonate and formate interact with each other in their binding to the Qв-protein and their interference with photosynthetic electron transport.

X-Ray Structure Analysis of a Cyanoacrylate Inhibitor of Photosystem II Electron Transport

1991 ◽  
Vol 46 (1-2) ◽  
pp. 93-98 ◽  
Author(s):  
Helen G. McFadden ◽  
Donald C. Craig ◽  
John L. Huppatz ◽  
John N. Phillips
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Chlorophyll Concentration ◽  
Photosynthetic Electron Transport ◽  
Hill Reaction ◽  
Ps Ii ◽  
X Ray ◽  
High Affinity ◽  
Modelling Studies ◽  
Intramolecular Hydrogen

Abstract X-ray crystallographic data for the highly potent cyanoacrylate photosynthetic electron transport inhibitor, (Z)-ethoxyethyl 3-(4-chlorobenzylamino)-2-cyano-4-methylpent-2-enoate, are presented. This compound has a particularly high affinity for the photosystem II (PS II) herbicide receptor with a p I50 value of 9.5 (in the Hill reaction under uncoupled condi­tions with a chlorophyll concentration of 0.1 μg/ml). Data regarding the structure of small li­gands, such as this potent cyanoacrylate, which bind to the site with high affinity may be used to provide the basis for modelling studies of PS II/herbicide complexes. The X-ray data presented confirm the Z-stereochemistry of active cyanoacrylates and demonstrate the pres­ence of a planar core stabilized by an intramolecular hydrogen bond between the ester car­bonyl oxygen and a benzylamino hydrogen atom. In order to assess the importance of the benzylamino -NH -group in this type of cyanoacrylate, analogues containing a methylene group in its place were synthesized and found to be 100-and 1000-fold less active as Hill inhibitors.

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